People who are unusually sleepy during the day for no apparent reason should be evaluated for obstructive sleep apnea and, if needed, undergo a diagnostic sleep study, according to a new clinical guideline.

Published today in the Annals of Internal Medicine, the guideline from the American College of Physicians (ACP) is based on reviews of peer-reviewed studies published from 1966 through May 2013. The ACP’s review of the medical literature evaluated how effectively different types of sleep tests can diagnose sleep apnea.

In people with obstructive sleep apnea, breathing slows or briefly stops because the airway becomes blocked during sleep. The result is poor sleep and excessive daytime sleepiness. Obesity is the best-documented risk factor, according to the guideline.

“Obstructive sleep apnea is a serious health condition that is associated with cardiovascular disease, hypertension, cognitive impairment, and type 2 diabetes,” ACP President David Fleming, MD, said in a statement. “It is important to diagnose individuals with unexplained daytime sleepiness so that they can get the proper treatment.”

Obstructive sleep apnea affects about 10% to 17% of the US population, according to the ACP. Estimates vary because researchers have used different criteria to define the condition in clinical studies.

Clinical symptoms include unintentionally falling asleep, daytime sleepiness, unrefreshed sleep, fatigue, insomnia, and snoring. For patients with these signs and no other potential causes of obstructive sleep apnea—thyroid disease, gastroesophageal reflux, or other respiratory conditions, for example—the guideline recommends a sleep study.

However, polysomnography is expensive and requires specialized equipment and personnel. For patients without access to a sleep laboratory and who don’t have other chronic medical conditions, the ACP recommends portable sleep monitors that can be used at home or in a hospital.

Fleming said diagnosing obstructive sleep apnea is in line with the ACP’s High Value, Cost-Conscious Care Initiative, which addresses providing quality care while reducing unnecessary costs.

“Prior to diagnosis, patients with obstructive sleep apnea have higher rates of health care use, more frequent and longer hospital stays, and greater health care costs than after diagnosis,” he said.